Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Process of making developer composition
Reexamination Certificate
2002-05-20
2004-06-15
Chapman, Mark A. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Process of making developer composition
Reexamination Certificate
active
06749980
ABSTRACT:
BACKGROUND
The present invention is generally directed to toner processes, and more specifically, to chemical processes which involve the aggregation and fusion of latex, colorant like pigment, or dye, and additive particles into toner particles, and wherein there is selected a surfactant free, or substantially surfactant free colorant dispersion, and which dispersion is comprised of, for example, a surface modified colorant dispersed in water. In embodiments the surface modified colorant, like pigment, includes a colorant containing at least one attached hydrophilic organic segment or group, and which group can be, for example, a carboxylic acid, a sulfonic acid, a sulfophenylaryl like sulfophenyl, a carboxy aryl, like carboxy phenyl, a sulfonamide, and the like. After mixing the colorant dispersion with a latex, the resulting blend is optionally stirred and heated to a temperature below the resin Tg, resulting in aggregates, followed by heating above the latex resin Tg to fuse the colorant and latex resin, thereafter isolating the toner product wherein there are generated toner compositions with, for example, a volume average diameter of from about 1 micron to about 25 microns, and more specifically, from about 2 microns to about 12 microns, and a narrow particle size distribution of, for example, from about 1.10 to about 1.33, and more specifically, a size distribution of about 1.11 to about 1.25, the size and size distribution being measured by a Coulter Counter without the need to resort to conventional pulverization and classification methods. Furthermore, in embodiments there can be enabled minimum washings, for example about 2 to about 4 washings to provide a suitable toner triboelectrical charge such as greater than about 20 &mgr;C/g at 20 percent RH. The toners generated can be selected for known electrophotographic imaging and printing processes, including digital color processes. More specifically, the toners generated with the processes illustrated herein are especially useful for imaging processes, especially xerographic processes, which usually prefer a toner transfer efficiency. Also, the toners obtained with the processes illustrated herein can be selected for digital imaging systems, printing processes, and color processes wherein images with high resolution and excellent image uniformity result.
In embodiments of the present invention an organic chelating may be utilized to freeze or stabilize the aggregates particle size during coalescence in the presence of a base of, for example, sodium hydroxide.
REFERENCES
In xerographic systems, especially color systems, small sized toners of from about 2 to about 8 microns can be important to the achievement of high image quality for process color applications. It may also be important to have a low image pile height to eliminate, or minimize image feel and avoid paper curling after fusing. Paper curling can be particularly pronounced in xerographic color processes primarily because of the presence of relatively high toner coverage as a result of the application of three to four color toners. During the fusing step, moisture escapes from the paper due to high fusing temperatures of from about 120° C. to about 200° C. In the situation wherein only one layer of toner is selected, such as in one color black or highlight color xerographic applications, the amount of moisture driven off during fusing can be reabsorbed by the paper and the resulting print remains relatively flat with minimal paper curl. In process color where toner coverage is high, the relatively thick toner plastic covering on the paper can inhibit the paper from reabsorbing the moisture, and cause substantial paper curling. These and other imaging shortfalls and problems are avoided or minimized with the toners and processes of the present invention.
Also, it may be desirable to select certain toner particle sizes, such as from about 2 to about 10 microns, with a high colorant, especially pigment loading, such as from about 4 to about 15 percent by weight of toner, so that the mass of toner necessary for attaining the desired optical density and color gamut can be significantly reduced to eliminate or minimize paper curl. Lower toner mass also ensures the achievement of image uniformity. However, higher pigment loadings, for example, of about 10 to about 20 percent by weight of toner may adversely affect the charging behavior of toners. For example, the charge levels may be too low for proper toner development or the charge distributions may be too wide and toners of wrong charge polarity may be present. Furthermore, higher pigment loading may also result in the sensitivity of charging behavior to charges in environmental conditions such as temperature and humidity. Toners prepared in accordance with the processes of the present invention minimize, or avoid these disadvantages.
There is illustrated in U.S. Pat. No. 4,996,127, the disclosure of which is totally incorporated herein by reference, a toner of associated particles of secondary particles comprising primary particles of a polymer having acidic or basic polar groups and a coloring agent. The polymers selected for the toners of the '127 patent can be prepared by an emulsion polymerization method, see for example columns 4 and 5 of this patent. In column 7 of this '127 patent, it is indicated that the toner can be prepared by mixing the required amount of coloring agent and optional charge additive with an emulsion of the polymer having an acidic or basic polar group obtained by emulsion polymerization. In U.S. Pat. No. 4,983,488, the disclosure of which is totally incorporated herein by reference, there is disclosed a process for the preparation of toners by the polymerization of a polymerizable monomer dispersed by emulsification in the presence of a colorant and/or a magnetic powder to prepare a principal resin component and then effecting coagulation of the resulting polymerization liquid in such a manner that the particles in the liquid after coagulation have diameters suitable for a toner. It is indicated in column 9 of this patent that coagulated particles of 1 to 100, and particularly 3 to 70 microns, are obtained. This process results, it is believed, in the formation of particles with a wide particle size distribution. In U.S. Pat. No. 4,797,339, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of toners by resin emulsion polymerization, wherein similar to the '127 patent certain polar resins are selected; and U.S. Pat. No. 4,558,108, the disclosure of which is totally incorporated herein by reference, discloses a process for the preparation of a copolymer of styrene and butadiene by suspension polymerization processes.
Emulsion/aggregation/coalescence processes for the preparation of toners are illustrated in a number of Xerox Corporation patents, the disclosures of each of which are totally incorporated herein by reference, such as U.S. Pat. No. 5,290,654, U.S. Pat. No. 5,278,020, U.S. Pat. No. 5,308,734, U.S. Pat. No. 5,370,963, U.S. Pat. No. 5,344,738, U.S. Pat. No. 5,403,693, U.S. Pat. No. 5,418,108, U.S. Pat. No. 5,364,729, and U.S. Pat. No. 5,346,797; and also of interest may be U.S. Pat. Nos. 5,348,832; 5,405,728; 5,366,841; 5,496,676; 5,527,658; 5,585,215; 5,650,255; 5,650,256; 5,501,935; 5,723,253; 5,744,520; 5,763,133; 5,766,818; 5,747,215; 5,827,633; 5,853,944; 5,804,349; 5,840,462; 5,869,215; 5,863,698; 5,902,710; 5,910,387; 5,916,725; 5,919,595; 5,925,488, and 5,977,210. The appropriate components and processes of the above Xerox Corporation patents can be selected for the processes of the present invention in embodiments thereof.
SUMMARY
It is a feature of the present invention to provide toner processes with many of the advantages illustrated herein, which advantages include, for example, less washing and thus a cost savings as compared to a number of known emulsion/aggregation toner processes, excellent projection efficiencies for the developed images.
A further feature of the present i
Chen Allan K.
Cheng Chieh-Min
Palazzo E. O.
Xerox Corporation
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